Dump valve for a circuit breaker pneumatic motor



Dee;l ll, 1951 E. c. GOODWIN DUMP VALVE FOR A CIRCUIT BREAKER PNEUMATIC MOTOR 2 SHEETS- SHEET 1 Filed May 14, 1948 Dec. 1l, 1951 E Q GOODWIN 2,578,349

DUMP VALVE FOR A CIRCUIT BREAKER PNEUMATIC MOTOR Filed May 14', 1948 2 SHEETSh-SHEET 2 Patented Dec. 11, 1951 DUMP VALVE FOR A CIRCUIT BREAKER PNEUMATIC MOTOR Edwin C. Goodwin, Canton, Mass., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application May 14, 1948, Serial No. 27,076

6 Claims. (Cl. 20o-82) The invention relates to circuit breakers, and more particularly to pneumatically operated high speed circuit breakers.

An object of the invention is the provision of an improved pneumatic circuit breaker operating mechanism of the cylinder piston type capable of eiecting high speed opening and reclosing of the circuit breaker.

Another object of the invention is to provide a pneumatic circuit breaker operating mechanism of the cylinder piston type comprising improved means for exhausting gas under pressure from the cylinder.

Circuit breakers for electrical power systems are required to operate at very high speed. This can be achieved by use of pneumatic operators of the cylinder piston type. Such operators require provision of dumping means for causing quick collapse of gas pressure in front of the piston tending to reduce the speed of movement thereof. Eiective dumping of compressed gas ,from the cylinder of a pneumatic operator of the cylinder piston type is of particular importance wherever it is desired to effect a rapid reversal of the movement of the piston. In case of reversal of the movement of the piston of a pneumatic motor supposed to operate at high speed, compressed gas should be dumped instantly from back ofthe piston preparatory to reversal of its movement.

In order to achieve dumping in a reliable uniform manner at each stroke of the piston requiring dumping, the point of time at which dumping is to take place must be predetermined with great accuracy, and dumping must take place rapidly thereafter. Reliability of operation calls further for a. self-sufiicient circuit breaker operating system, i. e., one wherein the time at which dumping is initiated and during which it is effected is Asolely dependent upon operating conditions of, and within, the pneumatic operator rather than upon any extraneous conditions or means as, for instance, upon conditions of electric circuits. or upon the presence of an electric relay. In addition to the foregoing reliability of operation requires that pressure conditions within the cylinder in the process of being vented be made the controlling factor as to maintaining the dumping means eiective upon initiation thereof, and as to permitting the dumping means to become ineffective to allow renewed relling of the cylinder with compressed gas. It is. therefore. another object of the invention to provide a self-suicient pneumatic circuit breaker operating mechanism of the cylinder piston type wherein the time at which dumping is initiated is determined by the relative position of piston and cylinder, and wherein the time during which the dumping means are maintained eiective is determined by the pressure that the gas in the-process of being dumped from the cylinder is capable to exert.

Different circuit breakers may have different mechanical systems having diierent masses, and may differ in many other respects, yet such different breakers may lend themselves to operation by a standard pneumatic operator, provided that the operator permits rapid dumping of compressed gas vfromback of the piston at diierent but exactly predeterminable times before the piston has completed its potential stroke. In case of closing of a circuit breaker the piston must be accelerated for a sufcient time to obtain the required speed of operation. Pressure of compressed gas upon the piston must also be maintained suiciently long to achieve safe latchingin of the mechanism provided for restraining the breaker in closed circuit position. -In order to permit rapid reversal of the movement of the piston gas pressure should not be maintained within the cylinder longer than necessary to meet these requirements. The point of time at which dumping is to be initiated is relatively critical and varies from circuit breaker to circuit breaker. It is, therefore. a further object of the invention to provide a, standard pneumatic circuit breaker operating system which can be applied to different circuit breakers and can readily be adjusted to the critical dumping time required for achieving best results in any particular application, and in which a self-adjustment of the time during which the dumping means are maintained effective in any particular application is achieved by controlling the dumping process by the pressure of the gas in the process of being dumped from the pneumatic motor.

Circuit breakers for electrical power systems comprise a linkage which is supposed to be latched-in when the piston is in closed circuit position so as to preclude the contacts of the circuit breaker to part. If a breaker is being closed by a pneumatic operator and the latching means fail to restrain the linkage and the contacts in closed circuit position, the contacts, which are biased to an open circuit position, are allowed to part. In that particular case parting of the contacts may occur at a very slow speed on account of a decelerating or dashpot action of the pneumatic operator. Parting of the contacts at a small speed results in prolonged arcing. In the case under consideration, the arcing time may well be suciently long to endanger both the system into which the breaker is connected as well as the breaker itself. It is, therefore, another object of the invention to provide means which become operative as often as latching-in is-to occur forv precluding damage to the breaker'aswell as to 'the system into which the breaker is connected in case of a latch failure.

Another object of the invention is the provision of an improved circuit breaker operating mechanism that comprises a linkage of the trip free type for operating the breaker and latching 4 l5, the parts by which linkage 2 is constituted are moved to their position shown in Fig. 1, which causes engagement of contacts 4 and 5 of breaker 3. Linkage 2 is now being latched-in by latching means which are fully described below, and thus linkage 2 restrains circuit breaker 3 in the closed position thereof against the bias of accelerating spring 5. When breaker 3 is closed, piston I5 and ram IE are free to move to their initial position `shown in Fig. 1 under the combined action of gravity and spring I6. There are certain instances where it is desired to close a circuit breaker manually without remeans for latching the linkageto restrain the breaker in closed circuit position, and that further comprises a pneumatic motor of the cylinder piston type having means for returning the piston to its initial position instantly upon completion of each closing operation.

Another object of the invention is to provide animproved pneumatic operating mechanism for circuit. breakers which lends itself to rapid reclosing duty, is simple, safe and reliable in operation, and inexpensive to manufacture. v`Other objects and advantages of the invention will become apparent from the following description when read in connection with the accomparis/ing drawing. in which; -v Fig. 1 is a view, partly in section, of a circuit breaker operating system embodying the present invention, the circuit breaker being shown somewhat diagrammatically;l

Fig.2 isa fragmentary,sectional View showing on aY larger scale the dump valveand the means for its1control; and l Figs. 3 to 5 show infront elevation three different-positions of the linkage by which the cir- .Guit ,breaker is operated and restrained in closed circuit position. .Referring now to Fig. 1y of the drawing, reference sign I vindicates generally a pneumatic motor of the cylinder piston type for operating the circuit breaker. The latter has been generally indicated by reference sign 3. Motor I and circuit breaker 3 are operatively related by a linkage which has been generally indicatedV by reference sgr`12` As diagrammatically shown, the circuit breaker 3 rcomprises apair of stationary contact members 4 and a movable contact member 5. vThe circuit breaker is biased to openv circuit position by means of accelerating" spring 5. The movable contact member 5 is supported by abreaker rod 1` which, in turn, is supported by lever Bfpivoted at 9j. Lever dis connected'to bellcrank lever l by means of operating rod'I I. Bellcrank lever Il ispivoted at 51 and forms part of linkage 2. "Motor I comprises the main casting I2 defining the lateral wall of the' operating cylinder of the motor, the topv element I3 'and the base element I4. PistonV 150i motori isfbias'ed in a downward direction by a helical 'spring I5 of Awhich one end restsagainst topV element I3, while its. other end restsagainst piston I5'. 'Base element I4 defines passage I1 Afor admitting gas under pressure from a suitable source of gas under pressure (not shown)A to the cylinder of motor l. The iiow of glasfunder pressure from saidy source to the cylindervof motor I may be controlled by a suitable valve Knot shown) preferably a solenoid operated valve.l Uponadmission of ygas under pressure to.

motor` Ipiston 4I5 is raised against the bias of spring, I6.A Piston I5 is provided with va ram or nlunger. I8 adapted` to cooperate with a roller I9 forming part oflir'ikage 2. Upon raisins ofpistorr sorting tothe operation of a pneumatic motor. To comply with thatV requirement, cylinder base I4 is providedV with. a bearing I4a, adapted to receive a plunger 16. Plunger 16 may be operated by means of a hand closing jack (not shown) to close circuit breaker 3.

Linkage 2 includes a bellcrank lever 20 pivoted at 2l and connected by pin 22 to toggle link 23. Lever 26 and toggle link 23 form a toggle 2li; 23 which is slightly off center in the closed position of the breaker (shown in Figfl) and which may be caused to collapse (as indicated in Figs. 3 and 4) on occurrence of a vfault lin the system into which the breaker is connected. The Ycenter pin 22 of toggle 2t, 23 supports the above referred to roller I9 adapted to be acted' upon by the plunger or ram it on piston I5. Thevri'ght end of link 23, as viewed in Fig. 1, is pivoted at 24 to a floating lever 25. Link 26 interconnects floating lever 25 and bellcrank lever Il). rlhe main latch 21 is pivotally supported at 28 "by stationary bracket 2d andacted upon by compression spring 30 of which one end bears against the main latch 21 while the other end bears against bracket 29. The lower end of main latch 21 is adapted to engage a latch plate 31| formingan integral part of bellcrank lever 2li. TheV upper end of main latch 21 constitutes an abutment 32 adapted to be engaged by a cooperating abutment 33 on latch 34. Latch 34 is pivotedat 35 and acted upon by acompression spring 36 tending to pivot it in a clockwise' direction about pin 35. As viewed in Fig. i, theY right side of latch 34 is provided with acam surface 31 adapted 'to'V engage a roller 38 carried by floating lever 25y by. means of pin 39. Upon release of roller 33 by cam surface 31, floating lever 25 is free to move under the action o accelerating spring 6, and this permits separation of contacts 4 and of circuit breaker 3.

When roller 33 has been released by cam surface 31, pin 39 moves from left to right along a substantially straightA path 'defined by guiding meansl til. rLatch 34 is also provided V with a straight cam surface 54 adapted to engage roller 38 during the interrupting process of the circuit breaker', as will? beseen` more' clearly as the description.v progresses. An-upperl cam surface 4I on latch 34 rests againsta latch 42 pivoted at 43 andacted upon byv biasing spring 44 tending to pivot it ina clockwise direction about pin 43. Latch 42 is held in position by a latch l5 engaging pin 46- on latch 42. Latch 45 is pivoted at 41V and biased in a counterclockwise direction by spring 48. The left arm of latch 45 is adapted to be pulled in an upwarddirection by a solenoid or a similar electroresponsive means 49, thus causing latch 45 to pivot about pin 41 in a clockwise direction. Lever 50 is pivotally mounted on pin 5I and adapted to engage lever 52 vwhich is pivotally mounted on pin 53.4 `Lever 52'is spring biased in a clockwisefdirection. Upon pivoting or lever d50`in a clockwisedirection about pin 5I (which may be effected manually), lever 52 is pivoted against the action of its biasing spring in a counterclockwise direction about pin 53. This causes latch 45 to be pivoted in a clockwise direction about pin 47 which, in turn, initiates separation of contacts 4 and 5 under the action of accelerating spring 6. The separation of contacts 4, 5 may be initiated in a similar way by energizing the relay or solenoid 49 in response to the occurrence of a fault in the system into which the breaker is connected.

A resetting compression spring 55 is arranged below the linkage and latching mechanism 2 of the breaker and biases bellcrank lever 25 in a clockwise direction. When the breaker is tripped as indicated in Fig. 3, the linkage and latch system 2 will be reset by the action of spring 55, thus assuming the position shown in Fig. 4.

In order to close the breaker, compressed gas is admitted to iluid motor I through passage I'l, thus causing piston I5 and ram I 8 to move in an upward direction. The closing force of motor I is applied to linkage 2 by engagement of ram I5 with roller I9. Fig. 4 shows the linkage mechanism in open position. Toggle 2G, 23, in moving up, rotates iloating lever 25 about pin 39 as a center. That rotary motion of lever 25 causes raising of the left side of link 25. This, in turn, causes bellcrank lever I to rotate in a clockwise direction about pin 57 as a center, pulling connecting rod II down and breaker rod l up, thereby closing the breaker against the action of accelerating spring 6.

As mentioned above, tripping may be initiated either mechanically by raising the left end ci lever D or electrically by energizing trip solenoid 49 operable in response to predetermined circuit conditions.l The armature of trip solenoid 49 lifts latch 45 against the reaction of cam latch 42. The resulting clockwise rotation of latch 45 about pivot 41 releases pin 46 on latch 42. rlhus latch 42 is free to rotate under the action of large latch 34 applied through upper cam surface 4I Latch 42 thereby slides oi large latch 34 as large latch 34 starts to rotate in a counterclockwise direction about pin 35 under the action of roller 38 which is acted upon by the powerful accelerating spring 5. The counterclockwise rotation of latch 34 against the bias of spring 35 permits the top end of iloating lever 25 to move to the right. As pin 39 on lever 25 moves to the right it slides in guiding means 45. That movement of lever 25 and pin 39 permits parts '1, 8 and I I of breaker 3 to move to open circuit position.

Rotation of latch 34 in a counterclockwise direction about pin 35 causes abutment 33 to engage abutment 32 on main latch 2l, thereby rotating main latch 2l in a clockwise direction about pin 28. Thus main latch 2l becomes disengaged from latch plate 3| on bellcrank lever 2 I.

Fig. 3 shows the position of the parts of the linkage and latch system 2 shortly upon initiation of the tripping process but before completion thereof. Fig. 4 shows the position of the parts of the linkage and latch system 2 upon completion of the tripping process. At the beginning of the tripping process, pin 39 moves in guiding means 4l) from left to right. Upon release of latch plate 3i by main latch 21, resetting spring 55 causes a clockwise rotation of bellcrank lever 20 about pin 2I which, in turn, causes collapse of toggle 20, 23, resulting in a movement of pin 39 in guiding means 4U from the right to the left, as shown in Fig. 4. While pin 39 moves from left to right, and then back to the left, the

straight cam surface 54 of latch 34 rests against the top of roller 38. Upon return of pin 39 and roller 38 to their original left position, latch 34 drops in place under the action of compression spring 35. This allows the balance of the system. including latches 42 and 45, to reset, as shown in Fig. 4. With the parts oi the linkage and latch system 2 back in the position shown in Fig. 4, the operator is ready for the next closing operation.

A closing operation is completed when main latch 2l has engaged latch plate 3I. Then the supply of compressed gas may automatically be shut off. This may be achieved, for instance, by a limit switch (not shown) controlled by shaft or pin 2l. Assuming now that there is a main latch failure, i. e., that either the main latch 2 or the latch plate 3I are so badly damaged (either broken or Worn out) that they fail to restrain the breaker in the closed circuit position. The breaker will then reopen under the action of accelerating spring 5, but its opening movement might be relatively slow on account of the decelerating action, or dashpot action, of fluid motor I. Even if the supply of compressed air is shut ol from motor l and the lower side of the motor I is being vented to atmosphere by prior art venting means, the decelerating eilect of motor I might be too large and the speed of separation of the contacts 4, 5 too small to achieve a safe interruption of the circuit controlled by the breaker. The dumping means shown in Figs. l and 2 are, however, any danger in case of ing means 21 and 3I.

As shown in Figs. l and 2, dumping of air admitted through passage l'I to cylinder I2 may be eiected by a piston type valve which has been generally indicated by reference sign 53. Valve 53 comprises a cylindrical valve body 59 which forms an integral part of piston I5 of motor I. Valve element Eil is movably arranged within valve body 59 and biased to a closed position by means of helical spring 6I. Valve element 53 is in the shape of a piston and one end of spring 6I rests against the inner side thereof, while the other end of spring 6I rests upon the base or valve body 59. Piston I5 is provided with bores dening a passage 62 for admission of compressed gas from the portion of cylinder I2 situated below piston i5 to valve 53. The top of valve element 60 is provided with a valve stern 53 adapted to cooperate with an abutment 54 upon reaching by piston I5 of a predetermined position within working cylinder I2. Engagement of stem `83 and abutment 64 results in initial opening of valve 58 against the bias of spring 6I. Upon initial opening of valve 58 gas under pressure below piston I5 is free to flow through passage 62, the space within valve 5 8 above valve element BIJ and apassage 65 provided in piston I5. Compressed gas which is admitted through passage 65 to the portion of the cylinder I2 above piston I5 is quickly dumped from that space through a permanently open passage 65 in cover plate I3. Upon initial cracking of valve 53 by engagement of stem 63 and abutment 54 a high pressure zone forms on top of valve element 65 tending to maintain valve element 5D in its open position against the bias of spring 5 l. Thus valve element 60 remains safely in its open position when, as a consequence of the reversal of the movement of piston I5 under the action of spring I6, valve 58 is no longer positively kept open by engagement of stem 4t3 and abutment 54. In the complete failure of latchso enfective as to preclude position of valve ..55 shown in Figs. 1 and 2, valve element B shuts off passage 55 from passage 62 and as long .as this is the case valve 53 cannot be opened by any pressure of gas in passage 52.

Gas under pressure that vleaks to the top of valveelement 55 is allowed to leak out from there to .atmosphere through a permanently open passage B1 defined by coaxial bores Vin piston l5 and valve housing 59. Thus gas under pressure leaking to the upper surface of valve element ed is precluded from exerting' a valve opening pressure k.upon valve element 50 at any point of time at which valve 58 is supposed to stay closed. Gas

vunder pressure that leaks to the lower side of valve element 55 is permitted to leak oil 'from there to atmosphere through a permanently `open leakage passage Ela. Passage 51a is 'defined by contiguous bores in piston l and 'valve housing 59. Thus gas lunder pressure leaking to the lower surface of valve element ed is precluded from exerting a valve closing pressure upon valve 'element 60 at a point of time at which valve 55 is supposed to stay open.

In addition to stem "63, valve element 65 is provided with a stem 68 cooperating with an abut-v ment 69 on cylinder base lli for closing valve 58 by positive action when piston l5 of motor I completes the end of its stroke in a downward direction.

Stem 63 is being engaged by abutment 64 close to the end of the closing stroke of piston l5. There must be sufcient power behind piston l5 to insure engagement of main latch 21 and latch plate 3l before compressed air can be dumped from fluid motor l. The moment the breaker 3 is restrained in closed circuit position by engagement of latching means 2i, 5l, any gas under pressure Within the cylinder l2 of motor l can instantly be dumped completely. It may be advisable, in order to achieve this end, to arrange a plurality of dumping valves 53 along the periphery of piston |45 and to arrange in a similar way aplurality of dumping ports 55 along the periphery of coverplate I3 though, in the drawing, but one such valve and one such port has been shown for the sake of clarity and Simplicity. If the latch mechanism 21, 3| performs properly upon closing of breaker 3 by fluid motor l, the breaker will remain in closed circuit position, but dumping of gas under pressure through passage 52, valve 58, passage 65 and passage 55 will nevertheless occur and result in .instantaneous high .speed reversal of the movement of piston I5 to its po-V sition shown in Fig. l. reached that position, is ready to perform another closing operation.

It will be readily observed from the foregoing that initial opening of dumping valve 58 occurs irrespective of the condition of the circuit controlled by the breaker, and that dumping does not depend upon the proper operation of any electrorespons'ive trip device operable in response to any fault condition of the system into which the breaker is connected. Where the operation of a Valve for dumping of compressed gas from the cylinder of a fluid operated circuit breaker oper-V ating motor is made dependent upon the presence of a fault condition in the electric system, the dumping valve does not afford any protection against the harmful consequences of a latch failure. Such an operating mechanism for circuit breakers would call for the provision of addi tional means for guarding against the harmful consequences of a latch failure, e. g., provision of an additional dumping valve which opens` au- Piston l5, upon having.

tomatically when the supply of compressed gas is shut off from the breaker operating motor. It is apparent that the arrangement vof the present invention requiring but one type of dumping valve is more simple, reliable in operation, and less expensive to'manufacture.

It will be observed that the pressure of lgas in passage 62, While able to maintain valve 58 in an open position upon initial opening of the valve, is unable vto effect -an initial opening of the vvalve. Initial opening of valve 58 requires its actuation by stem v(53.

The biasing action of spring 6i is extremely light. Therefore valve 58 Vwill remain open as long as there is but a vsmall amount Yof 'pressure in the lower portion of cylinder I2 in excess of atmospheric pressure.

Although but one embodiment of the inven tion has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein Without departing from the spirit of the invention or from the scope of the Vappended claims.

It is claimed and desired to secure by Letters Patent:

l. In an operating mechanism for circuit breakers, a motor operable by fluid under pressur'e and compr-ising a cylinder and a piston movably arranged therein; a source of fluid under pressure; means for admitting uid under pressure Ifrom said source to said cylinder Vto move said piston to a closed position; a collapsible linkage of the trip free type operated by said motor; latching means vfor restraining said linkage in a closed position; electroresponsive tripping means for releasing said latching means to cause collapse of said linkage; a rst spring means for resetting said linkage upon collapse thereof; a plunger operated by said piston for operating said linkage to close the breaker; means for permitting return of said plunger and of said piston from a closed position to an open position irrespective of the position of said linkage; a second spring means for returning said plunger and said piston from a closed position to an Open position; means including a piston type venting valve for said cylinder for permitting said second spring means to rapidly return `said plunger and said piston from a closed position to an open position to permit said first spring means to rapidly reset said linkage; said valve further including means for biasing said valve to a closed position and means operative only upon initial opening of said valve by separate initial valve opening means for maintaining said Avalve in an open position by the action of pressure of fluid escaping through said valve; and separate initial valve opening means operating under the action of fluid under pressure sup-plied to said cylinder from said source and adapted to be operative during each stroke of said piston from an open position to a closed position upon reaching by said piston of a predetermined intermediate position.

2. In an operating mechanism for circuit breakers, a motor operable by fluid under pressure and comprising a cylinder and a pistonV movably arranged therein; a source of fluid under pressure; means for admitting fluid under pressure from said source to said cylinder to move said piston to a closed position; spring means within said cylinder .for returning said piston to an open position; a collapsible linkage of the trip free type operated by said motor for closing 9, the breaker; means for restraining said linkage in Va closed position; electroresponsive tripping means forcausing collapse of 'said linkage; a ram on said piston separate k'from and cooperating with said linkage upon collapse thereof for reclosing the breaker; and means for instantly venting said cylinder not later than upon completion of each closing stroke of said piston; said venting means including a valve comprising a valve housing forming an integral part of said piston and a valve element movable relative to said valve housing, resilient means for biasing said valve element to a closed position, and means operative only upon initial moving of said valve element to an open position for maintaining said valve element in open position by the action oi' pressure of luid escaping from said cylinder; zigzag passage means through said piston and said valve housing for venting one side of said cylnder to atmosphere; a stationary abutment; and an abutment on said valve element cooperating with said stationary abutment for causing initial opening of said valve during each closing stroke of said piston.

3. In an operating mechanism for circuit breakers, a motor operable by fluid under pressure and comprising a cylinder and a piston movably arranged therein; a source of iiuid under pressure; means for admitting nuid under pressure from said source to said cylinder to move said piston to a closed position; spring means within said cylinder for returning said piston to an open position; a collapsible linkage of the trip free type operated by said motor for closing the breaker; means for restraining said linkage in a closed position; electroresponsive tripping means for causing collapse of said linkage; a ram on said piston separate from said linkage and cooperating with said linkage upon collapse thereof for reclosing the breaker; means for instantly venting said cylinder, said venting means including a piston type valve comprising a valve housing forming an integral part of said piston and a valve element movable relative to said valve housing, resilient means for biasing said valve element to a closed position, means denningapair of permanently open leakage passages for venting both sides of said valve element to atmosphere and means operative only upon initial moving of said valve element to an open position for maintaining said valve element in open position by the action of pressure of iluid escaping from said cylinder; a stationary abutment; and an abutment on said valve element cooperating with said stationary abutment for causing initial opening of said valve during each closing stroke of said piston.

4. A circuit breaker comprising relatively movable contacts; spring means for biasing said con-- tacts to an open position; a collapsible linkage of the trip free type for operating said contacts; latching means for restraining said linkage in a closed circuit position; a motor operable by iiuid under pressure to operate said linkage, said motor comprising a cylinder and a piston movably arranged therein; a source of i'luid under pressure; means defining a rst passage for admitting fluid under pressure from said source to sad cylinder to cause closing of said contacts: means defining a second passage for venting fluid under pressure from said cylinder to permit a rapid collapse of said linkage in case of opening of said contacts by said spring means on account of a failure of said latching means; and means ior controlling the ow of fluid through said second passage, said fluidflow controlling means including a valve forming a part of said piston; resilient means for biasing said valve to a closed position, .means voperative only upon initial opening of said valve for maintaining said valve in an open position by the action of li'uid in said second passage, zigzag passage means through said piston and said valve interconnecting said passages, and separate means secured to said piston for causing initial opening ofsaid valve irrespective of the condition of the circuit controlled by the breaken'said separate means being adapted to be controlled by the amount of the travel of said piston relative to said cylinder during a closing operation of said motor.

5. In an operating mechanism for circuit breakers, a motor operable by fluid under pressure and comprising a cylinder and a piston movably arranged therein: a source of fluid under pressure; means for admitting iluid under pressure from said source to said cylinder to actuate said breaker; a valve for rapidly venting iiuid from said cylinder, said valve comprising a valve housing forming an integral part of said piston, a valve element movable relative to said valve housing, resilient means for biasing said valve element to a closed position, and means operative only upon initial opening of said valve for maintaining said valve in an open position by the action of iluid being vented through said valve; zigzag passage means through said piston and said valve housing for venting one side of said cylinder to atmosphere, said zigzag passage means comprising two sections each extending substantially longitudinally through a part of said piston and interconnected by a third section extending substantially perpendicularly to the axes of said valve and of said piston through said valve housing; and means for causing initial opening of said valve, said initial opening causing means comprising a member secured to said valve and actuated by said piston in dependence upon the extent of travel of said piston relative to said cylinder.

6. In an operating mechanism for circuit breakers, a motor operable by fluid under pressure and comprising a cylinder and a piston movably arranged therein; a source of uid under pressure; means for admitting fluid under pressure from said source to said cylinder to actuate said breaker; a valve for rapidly venting fluid from said cylinder, said valve comprising a valve housing forming an integral part of said piston, a valve element movable relative to said valve housing, resilient means for biasing said valve element to a closed position, means defining a pair of permanently open leakage passages for venting both sides of said valve element to atmosphere, and means operative only upon initial opening of said valve for maintaining said valve in an open position by the action of fluid being vented through said valve; zigzag passage means through said piston and said valve housing for venting one side of said cylinder to atmosphere, said zigzag passage means comprising two sections each extending substantially longitudinally through a part of said piston and interconnected by a third section extending substantialy perpendicularly to the axes of said valve and of said piston through said valve housing; and means for causing intitial opening of said valve, said initial opening causing means comprising a member secured to said valve and actuated by said piston in dependence upon the ex- 1l `lient:l of travel ot said piston, relative. to said Number cylinders 2,048,550 i C. GOODWIN. 2,159,879 2,292,095 REFERENCES CITED 5 2,378,270 The following references are of record in the 2,381,336 ille of this patent: lgggg UNITED STATES IATENTS Number Namev l Date 1Q '28,651 Albright May 19, 1903 Number 944.485 Hicks Dec, za, 1909 647,572

Dewandre. ..-M M-, May 2.3. 19,39

Westervelt June 12, 1945 Coggeshall Aug. 7, 1945 Ludwig et al. May 28, 1946 Peek June 17, 1947 FOREIGN PATENTS Country Date Germany July '7, 1937 

